The specific aims of this proposal are designed to investigate the mechanisms by which the GATA transcription factor family regulates tissue-specific transcription during T lymphocyte and neuronal development. We originally identified a group of related transcription factors [the chicken GATA (cGATA) factor family]. More recent studies in a large number of laboratories have shown that homologs for each member of the family exists in all vertebrate species. These factors are themselves tissue-specifically regulated and bind to very similar cis- regulatory consensus sequences of genes expressed in a restricted set of tissues. Using the cloned transcription factor genes and cDNAs, as well as antibodies which recognize unique functional domains of these trans- activating proteins, we propose to investigate several aspects of GATA factor transcriptional activation. In the first series of experiments, we plan to empirically determine the biophysical parameters governing binding of the factors to their highest affinity site(s), and to then test whether binding sites encountered in genetically defined cis- regulatory sequences of neuronal and T cell genes bind the predicted factor family member. The role of GATA factor regulation in T lymphocyte differentiation and determination in hematopoietic cell culture models (cGATA-3 and mGATA-3) and in transgenic mice (mGATA-3) will be examined. We will ask whether the T lymphocyte-restricted transcription units encoding the T cell receptor delta gene, the HIV-1 genome and the murine lck gene are regulated by GATA-3, and whether or not the neuronal- specific nalpha acetylcholinesterase receptor gene is directly regulated by cGATA-2 and/or cGATA-3 in the CNS. We will also investigate the potentially determinative role(s) that specific GATA factors may play in T lymphocyte and CNS development in vivo, in chickens by examining the consequences of conditional GATA factor expression on lymphocyte differentiation (in transformed preB/preT cells) and in mice by examining the effects of targeted disruption of the mGATA-3 gene. The single copy Drosophila GATA factor gene will be studied (in order to incorporate the wealth of genetic background information available in this organism) to define the hierarchy of genes which regulate expression of the dGATA gene during embryonic development as well as to identify potential targets for its activity in the nervous system. These experiments will provide fundamental insight into how the earliest events which are specified by this family of transcription factors in the nervous system and in T cells may be achieved, and how the genetic processes which are regulated by this transcription factor gene family may go awry during altered embryonic development.